1. Field of the Invention
The present invention relates to an active electronically scanned array antenna, and, more specifically, to an active electronically scanned array antenna for hemispherical scan coverage.
2. Description of the Related Art
Radar systems use antennas to transmit and receive electromagnetic (“EM”) signals in various ranges of the EM band. While traditional radar systems used moving parts to physically point the antenna towards different target fields, modern radar systems use a passive electronically scanned array (“PESA”) in which a central EM signal is split into hundreds or thousands of paths by phase shift modules which send the signal into individual antenna elements (i.e. the antenna's electrical conductor material). A single radar unit can contain thousands of individual transmit receive modules (“TR”) rather than the single TR module of traditional radars, with each module functioning as an individual radar. Since transmission of the EM signal can be selectively delayed at each individual TR module, the electromagnetic signal, also called the “beam,” is steered without requiring movement of the antenna elements. In most radars, the TR module contains a receiver, power amplifier, a digitally controlled phase/delay element, and a gain element.
In an active electronically scanned array (“AESA”) each antenna element possesses its own EM signal source. As a result, each individual AESA antenna element can transmit a different EM frequency and the radar can capture a much more coherent radar profile of the target field. An AESA radar can steer the EM signal very quickly, and the TR modules can function in series to process a single project or function in parallel to complete several projects simultaneously. There are many additional advantages of AESA radars that can be found in the literature.
Despite these advantages, there are still significant obstacles to widespread adoption of AESA-based radar systems. For example, an AESA radar system using hundreds or thousands of TR modules can be prohibitively expensive.